The problem as I have witnessed it is during compression. The shock is too long when compressed, which means a lift kit is not the problem. Then again, I'm the only person breaking them.

Which Rancho's are you going to buy ? They don't make any that are the correct length for the Xterra.

I have the stock shocks back on now, and can't feel a difference...

I don't know Ian, maybe I am high, or maybe I don't understand independent suspensions. However, it appears to me, that a bumpstop in the form I am used to is mounted on the frame or body to reduce uptravel and keep the tire from rubbing the wheelwell. On downtravel the bumpstop doesn't come into play at all as the limits on downtravel usually are either the shock, the brakeline, or axle bind from the tube or CV. Maybe the Xterra is different.

Losing 1" of uptravel would make the truck tilt a bit more on wheel stuff. If you take a look at all those super-flexy rock buggies, land rovers, early broncos, etc., you will notice they ALL use longer bumpstops. Never seems to get it their way at all. On our Land Rovers, we have 2" bumpstops as stock, and either 4" or 6" bumpstops when we go aftermarket. Considering my truck would ramp about 750 stock, and 1200 or so with the SafariGard 3 link system and a 6" bumpstop, I fail to see how the bumpstop causes "loss of travel" in any area where it matters. As I said, perhaps the X is different and you can enlighten me.

As for springs that limit bottoming, I think you are grossly overestimating what is necessary. If you look at the problem logically, you will see that the most any one spring would have to manage on flat ground, would be the entire sprung weight on either the front or the rear. In offroading situations you can add an additional 30% for weight tranfer for uphill or downhill traversing. So if we had a theoretical 400 pound truck that was 100 pounds per axle, we'd need each spring to be able to bear the load of 200 pounds plus 30%. You'd then need a torsion bar that was capable of sustaining about 260-300 pounds of load. You'd then need a shock which could damp this amount of load over the deflection of the spring.

In the case of my Rover, each rear spring needs to handle approx. 2500 pounds over its 9" of flex before the spring goes into coil bind. That means a 275# spring will offer me the correct ride without danger of bottoming on static loads. However when ballistic loads are added I need more. So I run a variable rate spring of 275-330#. My bumpstops are long enough to keep my shocks from hitting bottom which is the way the system should work. So if my truck falls off a 2 foot ledge, the spring will compress to take up the slack until it runs out of room, then the axle hits the bumptstop, and the shock is about 1.5" from full collapse height. The springs rebound, the shocks damp down the spring and the truck returns to normal ride height.

In your case, your bumpstop is too short to protect your shock from collapsing all the way. You've gone to a slightly longer shock and this kind of failure is common when that happens. We use a wooden shim on our trucks behind the normal bumpstop when we add slightly longer shocks. When we go to much longer shocks, we use a much longer bumpstop. For an example, visit the page of Chris Hinkle (http://www.geocities.com/~defender110/). If you click on the "Coil-Over" button you will see his 6" bumpstops. But if you click into the "Yellow D90" and "White D90" you will see what kind of flex he still has with those bumpstops you claim are so limiting.

-P

Here's a thought... It seems to me that on a solid axle, a longer bumpstop can limit droop on the opposite side imposing an artificial fulcrum point in relation to the frame.

???

Quite correct. However on a solid axle truck you have a lever of about 2 feet (bumpstop fulcrum to tire on same side) with about 2000-2500 pounds of weight on it, acting to extend a shock on the other side of the axle. Unless the user specifically modifies the system, the springs are not retained and so it is very easy to get that side to droop. In an independently sprung truck you have no such lever and droop is controlled only by wieght on that corner.

-P

Ian,

Just curious, how many offroad miles did your front shocks have on them before the first one broke?

Maybe I better carry my stockers for spares.

I don't know.. I was just trying to talk like I knew something and ended up talking out of my ass again..

Seriously though, I do want to improve the ride on my minivan.. Considering how shitty our roads are here, I know I could use it..

Hmmm.. What to do..

Post the model number you have.

Probably the 5188, which is 8.40" compressed and 12.49 extended according to Rancho.
I have the 9188's here and they have the same measurement (according to Rancho).

They measure to the bottom of the stud mount, not to the center of the bushing, so the shock is a bit too long. It's also too short at full droop with an aftermarket lift...

Yup Send me a set when you get them done.

The 9188 and 5188 are the same length compressed and extended. Rancho's whole numbering scheme works that way.

The trick is getting 5 inches of travel in a shock that has a body only 5 inches long. Very hard to do with a piston and valving taking up room.

Thanks for the clarifications Ian. As I said, I am somewhat ignorant with independent suspensions so I try to preface my comments that way. Better than talking out my ass.

If Bilstein advertises this shock as correct length then I see your problem. When you guys do lifts, do you extend the shocks like we do on solid axles?

-P

Lift on an IFS vehicle can happen two ways.
First, everything can be moved away from the frame X inches to achieve X inches of lift. Trailmaster started this way back in 1986 with their 4" kits for Toyotas. It worked great, the lower control arm and diff were dropped 4 inches with brackets, and the spindle was replaced with one 4 inches taller. The upper control arm stayed where it was because Toyota routes the torsion bar into the upper arm. All of the stock geometry remained, and the only thing that changed was the driveshaft angle from the transfer case.

Here's my old 88 with the Trailmaster lift...


This is tricky to do with a Nissan (or Isuzu) because the torsion bar is mounted to the lower arm, and it requires that the back end of the torsion bar be lowered as well, puttin git in harms way. Trailmaster does offer a kit for older Nissan frames.

The other option is to change the upper control arm and preload the torsion bar (what all the Xterra lifts do). This causes the arms to be at a steeper angle at static ride height, thus creating lift. The new upper arm is a different shape than stock allowing it to not touch the bumpstop as the stock arm would at the same angle. This gives the suspension more overall travel, but only by adding droop. Upward travel limit remains unchanged, which is why the compressed length of the shock must be the same as stock.

The trick with the Xterra is that the stock shock is very short. It has 4 inches of travel but needs to be 8.625 inches long compressed and 12.4375 inches extended.

By going to a longer shock, with say 5 inches of travel, you run out of room in the shock body for the piston.

The best solution is to remove the upper shock mount, and replace it with a taller one, and run an overall longer shock. Still waiting for someone to release a bolt on, or weld on kit to do this.

OE Bilstein's are sh*t. We broke both of the rears ones on our GMC Yukon. I know of some people who broke their Bilstein's on Land Rovers and Chevy trucks. It is the 5100 Series (OE) that is crap. The 7100 and 9100, on the other hand, exhibit exceptional build quality. The 7100/9100 Series are the same ones used in Baja races; they have proven them selves to be very reliable. The best shock, in terms of build quality and price, is the Old Man Emu Nitrocharger shock. I have never heard of one complaint with these shocks.

Cheers,
Mel A.

F350 front shock mounts, they are about $20 at a Ford dealer...I can dig up the part number if you want them but these are used for lots of solid axle conversions.